Variable impedance device



May 31, 1949. A, HERZ vAnIABLE IMPEDANcE DEVICE Driginal -Filed Aug. 19,1942 s sheets-sheet 1 fg, AUM

x O e w NN my M Nw w@ hw NQ Nw. H1 M um lf w mum.. N a DN mw n?? m@ .6muw um NN J mw 1 A v h NNN. @MJ MWI .r r w W QT@ LQNNES WEF f m 4 mm w .H

May 31', 1949. A. HERZ 2,471,817

I VARIABLE IMPEDANCE DEVICE Original Filed Aug. 19, 1942 3 Sheets-Sheet2 @e 58k Y @5' @$959 J6 Wi@ I I I I I I I I I I l l l I I I I I I l I II I I I I I I I I I I I May 31, 1949,

A. HERZ VARIABLE' IMPEDANCE DEVI-GE Original .Filed Aug. 19, 1942 3Sheets-Sheet 3 .di J4 INVENTOR.

13k/MMM Patented May 31, 1949 UNITED STATES PATENT OFFICE VARIABLEIMPEDANCE DEVICE Alfred Herz, Chicago, Ill.

Original application August 19, 1942, Serial No.

455,283. Divided and this application December 16, 1943, Serial No.514,505

. vide a relatively high impedance in a winding by virtue of its linkinga closed magnetic circuit and for reducing the impedance of said windingby energizing another winding which completely surrounds the magneticcircuit and has a relatively low impedance so that when the otherwinding is energized both windings together offer a relatively lowimpedance to the flow of current therethrough and at the same time arecapable of permitting the ow of a relatively large amount of currenttherethrough.

Another object of the invention is to provide an improved core structurefor the above type of impedance device, including novel I adjustingmeans for adjusting air gaps in said core structure.

Another object of the invention is to provide an improved arrangement ofreactance winding and exciting winding on said core structure, andparticularly to provide an arrangement wherein the core structure formsa substantially closed magnetic circuit for the reactance winding butonly forms a non-continuous or partial magnetic circuit for the excitingwinding.

Other objects, features, and advantages of my invention will be apparentfrom the following detailed description of one preferred embodimentthereof.

In the accompanying drawings illustrating such embodiment:

Figure 1 is a diagrammatic view for the purpose of illustrating atypical use of my improved variable impedance device in an electriccontrol system;

Figure 2 is a view, in end elevation, of the variable impedance deviceconstituting the present invention;

Figure 3 is a view, in side elevation, of the variable impedance deviceshown in Figure 2;

Figure 4 is a top plan view of the variable impedance device shown inFigures 2 and 3;

Figure 5 is a detail sectional View taken along the line 5-5 of Figure3;

.Figure 6 is a perspective view of the magnetic core structure employedin the variable impedance device;

Figure 7 is a detail sectional view taken along the line 'l-I of Figure3; and

13 Claims. (Cl. 323-89) Figure 8 is a detail sectional view of one ofthe legs of the magnetic core structure shown in Figure 6.

The circuit diagram of Figure 1 serves to illustrate a particular fieldof utility of my improved variable impedance device in an electriccontrol system, wherein the variable impedance device performs aregulating function on a supply circuit. Figure 1 also constitutes aschematic wiring diagram of the variable impedance device. In this gureit will be observed that the reference character I0 designates thesource of alternating current, such as a cycle source. The source I0 isarranged to be connected by switches I I and I2 to load circuitconductors I3 and I4 to permit energization of the same. The loadcircuit conductors I3 and I4 are arranged to energize a load device,indicated generally at I5. In this particular instance the load deviceI5 is one which is particularly characterized by requiring theintermittent ow of relatively large amounts of current. A particularillustration of such a device is a spot welder which requires the flowof relatively large amounts of current during brief intervals.

The load device may `comprise a transformer, shown generally at I6,having a primary winding I1 arranged to be connected for energization tothe load circuit conductors I3 and I4. The transformer I 6 includes asecondary winding I8 which, as shown, is connected to energize the spotwelding electrodes I9.

The current ow to the primary winding Il of the transformer I6 andconsequently the current flow 5between the welding electrodes I9 can becontrolled in any suitable manner, now well known to those skilled inthe art. For illustrative purposes a conventional timer controller isshown at 2D. The timer 2D may comprise suitable control apparatus forpermitting the flow of current to the primary winding I'l in any desiredmanner. For example, the timer controller Z- may be arranged to permitthe ow of a predetermined number of .cycles or half cycles of thealternating current as conditions may warrant. The timer controller 20may be of the electronic type or of the contactor type as will bereadily understood.

Now when provision is made for energizing a. load device, such as a loaddevice I5, which requires that relatively large amounts of current flowperiodically, the voltage across the load circuit conductors I3 and I4,as well as across the conductors connecting the source I0 to theswitches I I and I2, varies more or less depending upon the stability ofthe system and its regulation. It often happens that other loadsconnected across the load circuit conductors. even when connectedbetween the source Iii and the switches II and I2, are adversely aectedby the application of the intermittent load applied by the Vdevice I5.This is particularly noticeable when a lighting load is connected acrossthe load circuit conductors. When the load device i5 is energized,

. there is the tendency for the voltage across the load circuitconductors to dip or decrease and consequently the lights tend to ickerin a corresponding amount.

As fully disclosed in the above parent application Serial No. 455,283,filed August 19, 1942, now Patent No. 2,401,156, I propose to rectifythis undesirable situation by automatically connecting across the loadcircuit conductors I3 and I4 an auxiliary load of such character thatthe regulation of the system is substantially unaffected by theenergization or deenergization of the load device I5. In this manner theeiective load supplied by the source is more or less constant in so faras the load device I is concerned, depending upon the degree ofcorrection that is desired. It has been found that it is unnecessary toapply an auxiliary load which has exactly the same characteristics asthe load device I5. The degree of correction that can be provided isdetermined by the economics of the situation and the amount of voltagedip which can be tolerated without being particularly objectionable. Theauxiliary load device is arranged to be automatically connected acrossthe load conductors l 3 and I4 so that the same is fully energized whenthe current flow to the load device I5 is reduced or ceases. As soon asthe load device I5 is again energized, energize.- tion of the auxiliaryload is reduced to a very low value.

The improved variable impedance device of the present invention can beemployed very advantageously as the above mentioned auxiliary loaddevice. This variable impedance device is indicated generally at 22. Itcomprises a magnetic core structure formed by side legs 23 and 2li andend legs 25 and 2t. The end legs 25 and 26 are arranged, as shown, toabut the adjacent sides of the legs 23 and 24. As will hereinafterappear the core structure is formed of laminated magnetic material.Around the leg 23 there is provided a winding 21 which is connected byconductors 23 and 33 for energizationto load circuit conductors I3 andI4. When the switches II and I2 are closed the Winding 21 is energized.However, since the winding 21 links a closed magnetic circuit formed bythe legs 23, 24, 25, and 2S, its impedance is relatively high and arelatively small amount of current ows therethrough..

An exciting winding 3| is provided around both legs 23 and 24 of themagnetic circuit and is connected by conductors 33 and 34 forenergization to the load circuit conductors I3 and I4. As willhereinafter appear, the winding 21 is formed in two sections and isdistributed uniformly along the leg 23. Also, as will be set forthhereinafter the exciting winding 3| extends along substantially the fulllength of both legs 23 and 24 and around the winding 21. However, forillustrative purposes the windings 21 and 3| have been illustrated asshown in Figure 1 to clarify the disclosure. These windings 21 and 3|are so connected and arranged that when the exciting winding 3| isenergized the alternating current control flux impedance winding 21 bothhave the same instantaneous direction of flow in the left hand leg 23 ofthe core structure.

Normally the exciting winding 3l is not energized. For the purpose ofenergizing it, switch means, shown generally at 35. are provided. Aswill hereinafter appear the switch means 35 are arranged to be closedwhen current ceases to flow to the load device I5.

When the switch means 35 are operated so as to energize the excitingwinding 3|, a substantial amount of current flows therethrough in viewof the fact that it does not link a closed magnetic circuit.Accordingly, the impedance of the exciting winding 3| is relatively low.The arrangement of the exciting winding 3i is such that on flow ofcurrent therethrough sufficient ux is generated by it to produce a highdegree of saturation in the leg 23 of the core structure while the iluxin the leg 24 is reduced. As a result, the impedance of the winding 21is materially reduced and the current iioW therethrough iscorrespondingly increased. The design of the variable impedance device22 is such that the combined ilow of the currents through the windings21 and 3| produces an effect which simulates that of the load device I5whenit is energized. However, the power factor of the current fiowing tothe variable impedance device 22 may be, and preferably is,substantially lower than the power factor of the current supplied to theload device I5. For example, the variable impedance device 22 may have apower factor at full load of the 4order of 5%. Because of this, theamount of actual power taken by the variable impedance device 22 is keptat a minimum. The net result of the auxiliary load or impedance device22 is such as to aiect the regulation of the power system or feedercircuit so that voltage dips caused by power drafts taken by the weldingor like load are within tolerable limits.

Any suitable formiof switch means 35 can be employed provided that it iscapable of satisfactorily handling the current ow to the excitingwinding 3I and can be controlled so as to substantially instantaneouslyfollow the changes in the iiow of current to the load device I5.

For example, the switch means 35 may comprise a pair of ignitionrectifiers 36 and 31 having control electrodes 38 and 39. As is wellknown the ignitrons 36 and 31 are of the mercury vapor type and each isarranged to conduct half cycles of one polarity. By connecting two ofthe rectifiers 35 and 31 in the conductor 34 in reverse, or backto-back,relation successive half cycles of the alternating current can beconducted. By controlling the excitation of the control electrodes 38and 39, the conductivity of the rectiers 3S and 31 is correspondinglycontrolled. For this purpose rectiers 4U and 4| are provided for therectifier 36 and the rectifiers 42 and 43 are provided for the rectifier31. The circuit between the rectifiers 4| and 42 is controlled by meansof separable contact members shown generally at 44 which are normallyheld in the closed position by a coil spring 45. An armature 46 isprovided for cooperating with a core 41 and winding 48 for opening thecontact members 44. The winding 48 is arranged to be energized from thesecondary winding 49 of a transformer, the primary winding of which is asingle turn and comprises the load circuit conductor I4. If desired,other means, such as electronic or electric valve control means, can beused in lieu of the contact members 44 and the associated operatingmeans.

In operation, as long as current is being supplied to the load device ilthere is a predetermined current ilow through the secondary winding 43of the current transformer and the armature II is attracted to the corel1. Contact members M are held in the. open position 'and the rectiers36 and 31 are rendered non-conducting. No current then flows throughtheexciting winding 3|, and only exciting current'iiows through the winding21.

As soon as the current ilow to the load device I5 ceases or isreduced'toa predetermined value, the amature 46 is' released and contact membersIl are closed. The circuit between the rectiflers 4| and-.42 is thenclosed and the rectiers -38 and 31 are then rendered conducting duringsuccesvsive half cycles 'as long as the contact members M remain in theclosed position;l The rectiiiers 36 and 31 thenconduct successive haltcycles of the valternating current and the exciting winding 3| isenergized. As previously described, the current flow through theexciting winding 3| is sumcient to increase the saturation oi themagnetic core structure and consequently the impedance of the winding 21is materially reduced. The auxiliary load or variable impedance device22 then has much the same effect on the power system as does the loaddevice l5. Consequently, the `range in variation of the voltage acrossthe load circuit conductors, caused by intermittent energization oi' theload device I5, is materially' reduced. The extent to which it isreduced will, of course, depend, as previously set forth, upon theeconomics of the situation and the degree of compensation that isrequired or the variation in voltage which can be tolerated. Il desired,the control of the auxiliary load device can be combined with thecontrol of the welder, as i'or example with the timer controller 20,although I consider the separate control through relay M-l8 preferable.

The details oi construction that are desirable in the impedance device22 are shown in Figures 2 through 8 of thev drawings, to which referencewill now be had. Y l

As shown more clearly in Figure 6 of the drawings, the magnetic corestructure is formed by the elongated legs 23 and 24 of laminatedmagnetic materialand members or legs 25 and 26 of the same material. Thebutt joints between the juxtaposed surfaces of the legs 23, 24, 25, and26 will be noted. This butt joint construction is provided so as topermit varying the effectiveness ofY the magnetic circuit by varying theair gaps bev tween the abutting members by means which will be describedhereinafter.

It will be observed in Figures 4 and 5 that the winding 21 is formed intwo sections which are .magnetic circuit. The winding 3| is coextensivewith the windings 21a and 21h.

AGenerally L-shaped clamp members 56 and 61 are provided-at the top andbottom of the core structure, as illustrated in Figures 2, 3, and 4 ofthe drawings, for the purpose of'holding the various parts in rigidspaced relation. The upstanding flanges of the L-shaped members 56 arespaced apart by a wood spacer 58 through which clamp bolts 59 extend.The spacer 58 can be extended lengthwise beyond the ends of the clampmembers 56 to provide a means for supporting or rigidly locating theentire assembly in a metallic tank, if desired.

The lower L-shaped clamp members 51 are spaced apart by a wood block 60and clamped in place by bolts 6|. Feet 62 extend outwardly from thedepending portions of the clamp members 51 to provide a footing for thedevice as it is mounted on the bottomof a tank. Longitudinally extendingbolts 63 serve to interconnect the parallel ilat portions of the clampmembers 5,6 and 51.

As previously indicated, the variable impedance device is intended to bemounted in a tank and to be covered with a suitable insulating and/orcooling liquidas is conventional in transformer practice. In order tofacilitate circulation of the insulating liquid the flat portions of theclamp members 56 and 51 are provided with large openings 64, Figure 4,some of which register with the spaces between the various windingsmounted on the core structure.

With a view to providing for adjusting the air Vgaps between the legsmaking up the main leg core structure, adjusting screws 61 yare providedin yokes 68 which extend between the upwardly and downwardly extendingportionsV of the clamp members 56 and 51 respectively. By tightening orloosening the adjusting screws 61 it is possible to decrease or increasethe air gaps between the juxtaposed surfaces of the legs making up themagnetic core structure. If desired, non-metallic spacer shims can ybeprovided between these juxtaposed surfaces to increase the rigidity ofthe j magnetic core structure.

Since various changes can lbe made in the foregoing construction ofvariable impedance device without departing from the spirit and scope ofthe present invention, it is understood that the As shown m Figure e ofthe drawings, suitable clamp members 53 are provided along the leg 23,and clamp bolts 54serve to hold them, and thereby the laminations makingup the leg 23, in4 place. 'Ihe laminations making up the legs 2l, 25,and 26 are held together by through bolts, the apertures forwhich areshown in Figure 6.

-subject matter set forth hereinbefore and shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim as my invention:

1. In a variable reactance device, the combination o`f a closed magneticcore structure, a reactance winding confined solely to one leg of saidcore structure, said reactance winding being adapted to be connected inshunt across an alternating current load circuit, and an alternatingcurrent saturating winding entirely surrounding said core structure andadapted to be energized from said alternating current load circuit, saidreactance winding and said saturating winding being so connected to saidsource of said alternating current load circuit that during thesuccessive alternations of thealternating current the reactance fluxgenerated by said reactance winding and the saturating flux generated bysaid saturating winding always have the same directions of flowV in saidone leg of the core structure.

`2. In a variable reactance device of the class described, thecombination of a generally rectangular magnetic core structure havingtwo sideV legs and tcp and bottom connecting legs, a reactance windingmounted on one of said side legs, said reactance winding being adaptedto be connected in shunt across an'alternating current load circuit, andan alternating current saturating winding wound entirely around both ofsaid side legs and adapted to be energized from said alternating currentload circuit, said reactance winding being conned solely to said oneside leg of said core structure and said saturating Winding being soconnected to said alternating current load circuit that for eachalternation of said current the saturating flux generated by saidsaturating winding and the reactance flux generated by said reactancewinding always have the same direction of ow in said one side leg'of thecore structure, whereby the saturating flux from the saturating windinghas a minimum tendency to generate a counter electromotive rforce insaid reactance winding.

3. A variable impedance device comprising, in combination, a generallyrectangular magnetic core structure, a reactance winding, the impedanceof which is to be varied, confined solely to one leg of said corestructure, and an alternating current exciting winding entirelysurrounding said core structure for varying the degree of saturation ofsaid core structure and thereby the impedance of said reactance Winding,said core structure, reactance winding and exciting winding being soconstructed and arranged that the alternating current reactance fluxproduced by said reactance Winding and the alternating current controlflux produced by said exciting winding always have the sameinstantaneous direction of ow in that leg of said core structure onwhich said reactance winding is mounted.

4. A variable impedance device comprising, in combination, a generallyrectangular core structure formed by legs of laminated magnetic materialand an air gap in series with said legs, an alternating currentreactance winding, the impedance of which is to be varied, confinedsolely to one leg of said core structure, and an alternating currentexciting winding surrounding opposite pairs of legs of said corestructure and adapted to be energized from the same source ofalternating current as said reactance winding for varying the degree ofsaturation of said core structure and thereby the impedance of saidreactance winding, said core structure and said reactance and excitingwindings being so conthe reactance winding to said one leg of the corestructure minimizes any tendency of the alternating current control fluxproduced by said exciting winding to generate a counter electromotiveforce in said reactance winding.

6. A variable impedance device comprising, in combination, a generallyrectangular core structure formed by legs of laminated magnetic materialdisposed in abutting relation with an air gap in series with said legs,a reactance winding,

the impedance of which is to be varied, Wound solely around one leg ofsaid core structure, and an alternating current exciting windingsurrounding opposite pairs of legs of said core structure and superposedover said reactance winding, said windings, being in inductive relation,said exciting winding adapted to be energized from a source ofalternating current for varying the degree of saturation of said corestructure and thereby the im-pedance of said reactance winding, saidcore structure affording a substantially continuous magnetic path forsaid reactance winding and a substantially non-continuous magnetic pathfor said exciting winding, the reactance ilux of said reactance windingand the control ux of said exciting winding both having the sameinstru'cted and arranged that when the exciting winding is energized thealternating current control ux produced by said exciting winding and thealternating current reactance flux Iproduced by said reactance windingboth have the same instantaneous direction of ow in that leg of saidcore structure on which reactance winding is mounted, the current flowthrough said exciting winding making up a substantial part of thephantom load of said variable impedance device.

'5. A variable impedance device comprising, in

combination, a closed magnetic core structure, an.

alternating current reactance winding, the impedance of which it to bevaried, confined solely to one leg of said core structure, and analternating current exciting winding entirely surrounding said corestructure and adapted to be energized from the same source ofalternating current as said reactance winding for varying the degree ofsaturation of said core structure and thereby the impedance of saidreactance Winding, said windings being in inductive relation, said corestructure affording a substantially continuous magnetic path for saidreactance Winding and a noncontinuous magnetic path for said excitingwinding, said core structure and windings being so constructed andarranged that 4the confinement of stantaneous direction of flow in thatleg of said core structure on which said reactance winding is mounted,and the confinement of the reactance winding to said one leg of the corestructure minimizing or preventing the alternating current control uxproduced by said exciting winding from generating a counterelectromotive force in any portion of said reactance winding.

'7. A variable impedance device comprising, in combination, a generallyrectangular core structure formed by legs of laminated magnetic materialdisposed in abutting relation, an alternating current reactance windingdivided into two sections and both mounted concentrically on only oneleg of said core structure, said two sections being spaced to permit acooling circulation therebetween, and an alternating current excitingwinding surrounding opposite legs of said core structure and superposedover said reactance winding, said exciting winding being adapted to beenergized from the same source of alternating current as said reactancewinding for varying the degree of saturation of said core structure andthereby the impedance of said reactance winding, said core structure andwinding being so constructed and arranged that the alternating currentcontrol ux produced by the exciting winding and the alternating currentreactance llux produced by the reactance winding both have the sameinstantaneous direction of flow in that leg of said core structure onwhich said reactive winding is mounted, the intermittent current flowthrough said exciting winding making up a substantial part ofthe phantomload of said variable impedance device.

8. In a variable impedance device for producing a phantom load, thecombination of a generally rectangular core structure formed by legs oflaminated magnetic material disposed in abutting relation, analternating current reactance Winding, the impedance of which is to bevaried, linking one leg of said core structure, and an alternatingcurrent exciting winding of D-shaped contour so located on said corestructure that a portion of the core structure is located between saidexciting winding and said reactance winding, said core structure andwindings being so constructed and arranged that the alternating currentcontrol ux of said exciting winding and the alternating currentreactance ux of said reactance winding both have the same instantaneousdirection of flow in that leg of said core structure on which saidreactance winding is mounted, said reactance winding and said excitingwinding both being supplied from the same load line whereby thealternating current ilow through both the reactance winding and theexciting winding at the time of excitation together make up the phantomload of the variable impedance device.

9. In a variable impedance device comprising. in combination, agenerally rectangular core structure formed by legs of laminatedmagnetic material, said legs being disposed in close proximity with airgaps between the juxtaposed surfaces of said legs, an alternatingcurrent reactance winding, the impedance of which is to be varied,conilned solely to one leg of said core structure and adapted to beconnected to a load line, an alternating current exciting windingsurrounding opposite legs o1' said core structure and adapted to beenergized from the same load line as said reactance winding for varyingthe degree of saturation of said core structure and` thereby theimpedance of said reactance winding, and adjusting means enabling saidair gaps between the juxtaposed surfaces of said core structure legs tobe increased or decreased, the alternating current vrlow through boththe reactance winding and the exciting winding at the time of excitationof the latter together making up, the phantom loadA oi the variableimpedance device.

10. In a variable impedance device for producing a phantom load on analternating current circuit in alternating sequence with a line loadthereon, the combination of a generally rectangular core structureformed by legs of laminated magnetic material, certain of said legsbeing disposed in close proximity to each other with small air spacesdefined between the juxtaposed surfaces of said legs, a reactancewinding, the impedance of which is to be varied, conilned solely to oneleg of said core structure and connected to said alternating currentcircuit, an a1- ternating current exciting winding surrounding oppositelegs of said core structure and also connected to said alternatingcurrent circuit, said exciting winding serving to vary the degree orsaturation of said core structure and thereby the impedance of saidreactance winding when said exciting winding is energized, thealternating current now through both `the reactance winding and theexciting winding at -the time of excitation together making up thephantom load of the variable impedance device, brackets secured to saidcore structure adjacent to said air gaps, and adjusting screws carriedby said brackets and operative to increase or decrease the size of saidair gaps.

11. In a variable impedance device for producing a phantom load on analternating current circuit in alternating sequence with a line loadthereon, the combination of a generally rectangular core structureformed by legs of laminated magnetic material disposed in abuttingrelation, an alternating current reactance winding divided into aplurality of sections mounted concentrically on only one leg of saidcore structure, said seclatter together making up the phantom load of lth-e variabler impedance device, the D-shaped contour of said excitingwinding establishing a relatively large oil circulating passagewaybetween said reactance and exciting windings along the other leg of saidcore structure.

12. In a variable impedance device for producing a phantom load on analternating current circuit in alternating sequence with a line loadthereon, the combination of a generally rectangular magnetic corestructure, an alternating current reactance winding and an alternatingcurrent exciting winding both mounted on said core structure, saidreactance winding being connected in shunt acrosssaid alternatingcurrent circuit and said exciting winding being adapted for connectionin shunt across said alternating current circuit in alternating sequencewith said line load, said core structure affording a substantiallycontinuous magnetic path for saidreactance winding and a non-continuousmagnetic path for said exciting winding, and said reactance windingbeing so disposed on said core structure that it is nonsymmetrical withrespect to said exciting winding.

13. In a variable impedance device, the combination of a generallyrectangular'magnetic core structure, an alternating current reactancewinding on saidcore structure, an alternating current exciting windingon said core structure, said core structure affording a substantiallycontinuous magnetic path for said reactance winding and a non-continuousmagnetic path for said exciting winding. and said reactance windingbeing so disposed on said core structure that it is non-symmetrical withrespect to said exciting winding.

ALFRED HERZ.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,563,354 Fortescue Dec. 1, 19251,724,968 Schelleng Aug. 20, 1929 1,870,093 Boyajian et al. Aug. -2,1932. 2,127,237 Sola Aug. 16, 1938 2,333,015 Kramer et al. Oct. 26,A194:3

FOREIGN PATENTS Number Country Date 376,867 Great Britain July 2.1, 1932

